Appending to UserDefaults Array (Swift)

I would suggest you to create a computed property for this purpose:

var intArray: [Int] {
    get {
        return UserDefaults.standard.array(forKey: "intArray") as? [Int] ?? []
    }
    set {
        UserDefaults.standard.set(newValue, forKey: "intArray")
    }
}

Now whenever you modify your intArray it will update its value in UserDefaults and whenever you call intArray it returns you the value from UserDefaults.

Not sure about what you need.

However this is how you add an empty array to UserDefaults

 UserDefaults.standard.set([Int](), forKey: "nums")

And this is how you

1. load the array from UserDefaults
2. add a value
3. save it again to UserDefaults

.

var nums = UserDefaults.standard.array(forKey: "nums") as! [Int]
nums.append(1)
UserDefaults.standard.set(nums, forKey: "nums")

Instead of this:

var intArray = UserDefaults.standard.array(forKey: "intArray") as! [Int]

do this:

var intArray = UserDefaults.standard.array(forKey: "intArray") as? [Int] ?? []

This will initialize the array to an empty array in the case that it does not yet exist in the defaults database (or if it's corrupt in some way that it won't resolve to an array of Ints).

Avoiding the use of as! here is good practice anyway, since otherwise you're going to crash on read if your defaults become corrupt.